JP6331257B2 - Method for evaluating powdering resistance of plated steel sheets - Google Patents
Method for evaluating powdering resistance of plated steel sheets Download PDFInfo
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本発明は、めっき鋼板の耐パウダリング性評価方法に係り、特に、合金化溶融亜鉛めっき鋼板の耐パウダリング性の高精度な評価方法に関する。 The present invention relates to a method for evaluating powdering resistance of a plated steel sheet, and more particularly, to a highly accurate method for evaluating powdering resistance of a galvannealed steel sheet.
従来、自動車、家電、建築材料等の鋼材製品における耐食性の向上を目的として、表面処理鋼板が広く使用されてきた。中でも、自動車用鋼板においては、防錆およびプレス成形性の観点から、合金化溶融亜鉛めっき鋼板（以下、「ＧＡ鋼板」という。）が多く使用されている。ＧＡ鋼板は、通常、鋼板を亜鉛浴中に浸漬した後、合金化熱処理を行うことで製造される。 Conventionally, surface-treated steel sheets have been widely used for the purpose of improving corrosion resistance in steel products such as automobiles, home appliances, and building materials. Among them, in an automotive steel sheet, an alloyed hot-dip galvanized steel sheet (hereinafter referred to as “GA steel sheet”) is often used from the viewpoint of rust prevention and press formability. The GA steel sheet is usually produced by immersing the steel sheet in a zinc bath and then performing an alloying heat treatment.
しかしながら、ＧＡ鋼板は、めっき層が実質的にＺｎ−Ｆｅ金属間化合物で構成されるため、硬く脆いという性質があり、プレス成形時の変形によって、表面の亜鉛めっきが粉末状に剥離する、いわゆる「パウダリング」が生じるという問題がある。パウダリングが発生すると、剥離しためっき粉が成形品に付着することによって、押込み疵、金型への損傷、塗装時の外観劣化等、様々な問題を誘発する。 However, the GA steel sheet has a property that it is hard and brittle because the plating layer is substantially composed of a Zn—Fe intermetallic compound, and the so-called galvanized surface peels off in a powder form due to deformation during press molding. There is a problem that "powdering" occurs. When powdering occurs, the peeled plating powder adheres to the molded product, thereby inducing various problems such as indentation flaws, damage to the mold, and appearance deterioration during painting.
ＧＡ鋼板の耐パウダリング性を評価する方法として、耐パウダリング性との間に良好な相関関係があるめっき層中のＦｅ濃度（以下、「合金化度」という。）を指標とする方法がある。しかしながら、合金化度を求めるためには比色法、発光法、吸光法等の化学分析を行う必要があり、この方法では時間およびコストが極めてかかるという欠点がある。 As a method for evaluating the powdering resistance of a GA steel sheet, there is a method using as an index the Fe concentration (hereinafter referred to as “alloying degree”) in the plating layer having a good correlation with the powdering resistance. is there. However, in order to obtain the degree of alloying, it is necessary to perform chemical analysis such as a colorimetric method, a luminescence method, an absorption method, etc., and this method has a drawback that it takes a lot of time and cost.
より簡易な方法として、プレス成形を模擬した簡易成形試験を行い実際に剥離しためっき量を測定する方法があり、これまでにも様々な提案がなされている。 As a simpler method, there is a method of measuring a plating amount actually peeled by performing a simple molding test simulating press molding, and various proposals have been made so far.
特許文献１には、ＧＡ鋼板に曲げ加工を施し、加工部にセロテープ（登録商標）を貼り付けた後にテープ内面に剥離付着した亜鉛粉末量を、蛍光Ｘ線分析等を用いて定量的に測定する方法が開示されている。 In Patent Document 1, the GA steel sheet is bent, and the amount of zinc powder that peels and adheres to the inner surface of the tape after a cello tape (registered trademark) is attached to the processed part is measured quantitatively using fluorescent X-ray analysis or the like. A method is disclosed.
また、特許文献２および３には、ＧＡ鋼板の曲げ試験または曲げ・曲げ戻し試験を自動化することにより作業の効率化を可能とした試験装置が開示されている。 Patent Documents 2 and 3 disclose test apparatuses that can improve work efficiency by automating a bending test or a bending / bending test of a GA steel sheet.
さらに特許文献４には、金型の形状を改良した円筒絞り試験を行い、側壁部のめっき剥離性を調査することによって、より実際の成形に近い条件で耐パウダリング性を評価する方法が開示されている。 Furthermore, Patent Document 4 discloses a method for evaluating powdering resistance under conditions closer to actual molding by conducting a cylindrical drawing test with an improved mold shape and investigating the plating peelability of the side wall. Has been.
特許文献１に記載の方法では、テープに付着しためっき量をＸ線分析により定量するため、時間およびコストがかかるという問題がある。また、特許文献２〜４に記載の曲げ試験および円筒絞り成形試験について、本発明者らが実施した詳細な調査から、下記のような問題があることが分かった。 In the method described in Patent Document 1, there is a problem that it takes time and cost because the amount of plating attached to the tape is quantified by X-ray analysis. Moreover, it turned out that the following problems exist from the detailed investigation which the present inventors implemented about the bending test and cylindrical drawing test of patent documents 2-4.
（ｉ）曲げ試験による耐パウダリング性評価
図１は、曲げ試験による耐パウダリング性評価結果の精度を示した図である。曲げ試験による耐パウダリング性評価においては、ＧＡ鋼板の曲げ試験を行い、曲げ部にテープを貼り付けて剥がした時のテープに付着しためっき剥離幅（ｍｍ）を耐パウダリング性の指標とした。
(I) Powdering Resistance Evaluation by Bending Test FIG. 1 is a diagram showing the accuracy of the powdering resistance evaluation result by the bending test. In the powdering resistance evaluation by a bending test, the GA steel sheet was subjected to a bending test, and the plating peeling width (mm) attached to the tape when the tape was attached to the bent portion and peeled was used as an index of the powdering resistance. .
なお、曲げ試験は、ＪＩＳ Ｚ ２２４８（２００６）で規定される、曲げ角度９０°のＶブロック法を用いて行い、押金具の先端部の半径は２ｍｍ、試験力は３０ｋＮ、試行回数は３回とした。また、供試材には、合金化度８．０〜１１．８％の板厚０．７ｍｍの２７０ＭＰａ級合金化溶融亜鉛めっき鋼板（鉄鋼連盟規格：ＪＡＣ２７０Ｄ）を用いた。 The bending test is performed using the V-block method defined by JIS Z 2248 (2006) with a bending angle of 90 °, the radius of the tip of the metal fitting is 2 mm, the test force is 30 kN, and the number of trials is 3 times. It was. Further, as a test material, a 270 MPa class galvannealed steel sheet (iron federation standard: JAC270D) having a degree of alloying of 8.0 to 11.8% and a thickness of 0.7 mm was used.
上述のように、耐パウダリング性とめっきの合金化度との間には密接な関係が存在する。しかしながら、図１を見ると、合金化度が９．６〜１１％の範囲において、めっき剥離幅に有意な差が認められない。また、結果に大きなばらつきが存在し、精度の高い評価方法とは言い難い。 As described above, there is a close relationship between the powdering resistance and the degree of alloying of plating. However, when FIG. 1 is seen, in the range of 9.6 to 11% of alloying, a significant difference is not recognized by the plating peeling width. In addition, there are large variations in the results, and it is difficult to say that the evaluation method is highly accurate.
（ｉｉ）円筒絞り成形試験による耐パウダリング性評価
図２は、円筒絞り成形試験による耐パウダリング性評価結果の精度を示した図である。円筒絞り成形試験は、半径５０ｍｍの円板状のＧＡ鋼板に対して、外縁部を中空円筒状のダイスおよびホルダーを用いて押さえ圧１２ｋＮで押さえ、中心部を半径２５ｍｍの円筒形パンチでダイスの方向へ１９ｍｍ進行させて、ＧＡ鋼板を外縁にフランジを有する円筒形容器に成形することで行った。試行回数は３回とした。
(Ii) Powdering Resistance Evaluation by Cylindrical Drawing Test FIG. 2 is a diagram showing the accuracy of the powdering resistance evaluation result by the cylindrical drawing test. In the cylindrical drawing test, the outer edge of a circular GA steel plate with a radius of 50 mm was pressed with a pressing pressure of 12 kN using a hollow cylindrical die and a holder, and the center of the die was pressed with a cylindrical punch with a radius of 25 mm. The steel plate was advanced 19 mm in the direction, and the GA steel plate was formed into a cylindrical container having a flange on the outer edge. The number of trials was three.
上記の曲げ試験と同様に、供試材には、合金化度８．０〜１１．８％の板厚０．７ｍｍの２７０ＭＰａ級合金化溶融亜鉛めっき鋼板（鉄鋼連盟規格：ＪＡＣ２７０Ｄ）を用いた。そして、精密量りを用いて成形前後での重量を測定し、成形に伴うめっき剥離量を算出し、耐パウダリング性の指標とした。 Similar to the above bending test, a 270 MPa grade galvannealed steel sheet (iron federation standard: JAC270D) having a sheet thickness of 0.7 mm and an alloying degree of 8.0 to 11.8% was used as a test material. . And the weight before and behind shaping | molding was measured using the precise weighing, the plating peeling amount accompanying shaping | molding was calculated, and it was set as the index of the powdering resistance.
図２を見ると、合金化度の増加に伴い、めっき剥離量が増加する傾向は認められるものの、測定結果にばらつきが大きく、精度の高い評価方法とは言えないことが分かる。 As can be seen from FIG. 2, although the tendency to increase the amount of plating peeling with the increase in the degree of alloying is recognized, the measurement results vary widely and cannot be said to be a highly accurate evaluation method.
本発明は、上記現状に鑑みてなされたもので、簡易かつ高精度なめっき鋼板の耐パウダリング性評価方法を提供することを目的とする。 This invention is made | formed in view of the said present condition, and it aims at providing the powdering-proof evaluation method of a plated steel plate simple and highly accurate.
本発明者らは、上記の課題を解決するため、鋭意研究を行った結果、以下の知見を得るに至った。 As a result of intensive studies to solve the above-mentioned problems, the present inventors have obtained the following knowledge.
（ａ）曲げ試験を行う場合、ＪＩＳ Ｚ ２２４８（２００６）で規定されるように、試験片を押金具と支えまたはＶブロックとで押曲げるのが一般的である。めっき鋼板のパウダリングは圧縮変形により生じるため、一般的な曲げ試験では、曲げ部の内側、すなわち押金具と試験片との接触点およびその付近でパウダリングが生じることになる。 (A) When a bending test is performed, it is common to press and bend the test piece with a metal fitting and a support or a V block as defined in JIS Z 2248 (2006). Since powdering of the plated steel sheet is caused by compressive deformation, in a general bending test, powdering occurs inside the bent portion, that is, at the contact point between the metal fitting and the test piece and in the vicinity thereof.
（ｂ）剥離しためっきが曲げ成形中に金具で押込まれ、高い面圧を受けると、金具または試験片にめっき粉が再付着してしまう。そのため、耐パウダリング性が適切に評価できていないと考えられる。 (B) When the peeled plating is pushed in by the metal fitting during bending and receives a high surface pressure, the plating powder is reattached to the metal fitting or the test piece. Therefore, it is considered that the powdering resistance has not been properly evaluated.
（ｃ）円筒絞り成形試験を行う場合、パウダリングは成形された円筒形容器の側壁部および外縁のフランジ部で生じる。側壁部およびフランジ部は円筒絞り成形の際、ポンチとダイスおよびダイスとホルダーとで強い面圧を受けることになるため、剥離しためっき粉の再付着が起きてしまう。さらに、側壁部はポンチまたはダイスと摺動するため、それに起因しためっきの燐片状の剥離（以下、「フレーキング」という。）が生じる可能性がある。そのため、パウダリングに起因した剥離量のみを適切に評価できていないと考えられる。 (C) When performing a cylindrical drawing test, powdering occurs at the side wall and the outer flange of the molded cylindrical container. The side wall portion and the flange portion are subjected to a strong surface pressure by the punch and the die and the die and the holder when the cylindrical drawing is performed, so that the peeled plating powder is reattached. Further, since the side wall portion slides with the punch or the die, there is a possibility that the flake-like peeling of plating (hereinafter referred to as “flaking”) due to the sliding occurs. Therefore, it is considered that only the amount of peeling due to powdering cannot be properly evaluated.
（ｄ）めっき鋼板の表面にパウダリングを生じさせるためには、種々の工具を用いて成形加工を行うこととなる。その際、めっき鋼板の工具で挟持される部分でパウダリングが生じるような成形方法を用いてめっき剥離量を測定するのでは、めっき粉の再付着によりめっき鋼板の耐パウダリング性を正しく評価することはできない。 (D) In order to generate powdering on the surface of the plated steel sheet, various types of tools are used for forming. At that time, when measuring the amount of plating peeling using a forming method in which powdering occurs at the part sandwiched between the tools of the plated steel sheet, the powdering resistance of the plated steel sheet is correctly evaluated by reattaching the plating powder. It is not possible.
（ｅ）すなわち、成形に際して工具で挟持される部分でパウダリングがほとんど発生しないような条件で成形加工を行うことで、めっき粉の再付着等の問題が生じずに耐パウダリング性を適切に評価できるようになる。 (E) In other words, by performing molding under conditions such that powdering hardly occurs at the part that is sandwiched between tools during molding, the powdering resistance can be appropriately improved without causing problems such as reattachment of plating powder. Can be evaluated.
本発明は、上記の知見を基礎としてなされたものであり、下記のめっき鋼板の耐パウダリング性評価方法を要旨とする。 The present invention has been made on the basis of the above findings, and the gist thereof is the following method for evaluating the powdering resistance of a plated steel sheet.
（１）めっき鋼板に工具を用いて成形を施して、該めっき鋼板の表面の少なくとも一部に圧縮ひずみを生じさせることでパウダリングを発生させ、めっき剥離量を測定することによりめっき鋼板の耐パウダリング性を評価する方法であって、
前記めっき剥離量を測定する箇所は、成形過程において該工具によって挟持されない箇所であり、
円板状に加工しためっき鋼板を、逆円錐形のダイスと先端形状が半球状のパンチとでコニカルカップ状にプレス成形することで、前記めっき鋼板に前記成形が施されることを特徴とするめっき鋼板の耐パウダリング性評価方法。
（２）前記成形過程において前記工具によって挟持されない箇所に、圧縮ひずみ量が９％以上の領域があることを特徴とする上記（１）に記載のめっき鋼板の耐パウダリング性評価方法。
(1) Forming a plated steel sheet with a tool, generating a compressive strain on at least a part of the surface of the plated steel sheet, generating powdering, and measuring the amount of plating peeling, thereby improving the resistance of the plated steel sheet. A method for evaluating powdering properties,
Point of measuring the plating peeling amount Ri portions der not held by the tool in the molding process,
The plated steel sheet was processed into a disk shape, die and tip shape of the inverted cone shaped by press-molding the conical cup and hemispherical punch, characterized in Rukoto said forming is performed on the plated steel sheet Method for evaluating powdering resistance of plated steel sheet.
(2) The method for evaluating the anti-powdering property of a plated steel sheet according to the above (1), wherein there is a region where the amount of compressive strain is 9% or more at a location not sandwiched by the tool in the forming process.
（３）前記円板状に加工しためっき鋼板と前記パンチとの間に、前記めっき鋼板より板厚の厚い円板状の鋼板を介在させた状態でプレス成形を行うことを特徴とする上記（１）または（２）に記載のめっき鋼板の耐パウダリング性評価方法。 ( 3 ) The above-mentioned, characterized in that press forming is performed with a disk-shaped steel plate thicker than the plated steel plate interposed between the plated steel plate processed into the disc shape and the punch ( The method for evaluating powdering resistance of a plated steel sheet according to 1) or (2) .
本発明によれば、めっき鋼板の表面にパウダリングを発生させる成形を行うに際して、剥離しためっき粉の再付着が生じることがないため、めっき剥離量を簡易かつ高精度に測定することが可能である。 According to the present invention, when performing forming that generates powdering on the surface of the plated steel sheet, the peeled-off plating powder does not reattach, so that the amount of plating peeling can be measured easily and with high accuracy. is there.
１．めっき鋼板の成形
めっき鋼板にパウダリングを発生させるためには、めっき鋼板の表面の少なくとも一部に、圧縮ひずみ量が９％以上となる領域を形成するような成形を施さなければならない。圧縮ひずみ量を９％以上とする理由は以下の通りである。
1. Forming of plated steel sheet In order to generate powdering in the plated steel sheet, it is necessary to form such that a region where the amount of compressive strain is 9% or more is formed on at least a part of the surface of the plated steel sheet. The reason why the amount of compressive strain is 9% or more is as follows.
ＪＩＳ Ｚ ２２４９（２０１０）で規定されるコニカルカップ試験方法を用いて、めっき鋼板をコニカルカップ状に成形し、成形品にテープを貼り付けることで、パウダリングが生じる箇所を特定した。そして、実験と同じ条件の有限要素法の数値解析を行い、実験でパウダリングが生じた箇所における最小主ひずみを読み取ったところ、圧縮ひずみ量が９％であることが分かった。 Using a conical cup test method defined in JIS Z 2249 (2010), a plated steel plate was formed into a conical cup shape, and a portion where powdering occurred was specified by attaching a tape to the molded product. Then, numerical analysis of the finite element method under the same conditions as in the experiment was performed, and when the minimum principal strain at the location where powdering occurred in the experiment was read, it was found that the amount of compressive strain was 9%.
上述のように、成形過程において、パウダリングが生じた個所が工具によって高い面圧を受けると、剥離しためっき粉がめっき鋼板または工具に再付着してしまい、正確なめっき剥離量の測定が困難になる。 As described above, when the part where powdering occurs in the forming process is subjected to a high surface pressure by the tool, the peeled plating powder reattaches to the plated steel sheet or tool, making it difficult to accurately measure the amount of plating peeling. become.
したがって、本発明に係る耐パウダリング性評価方法においては、成形によるめっき鋼板の表面の圧縮ひずみ量が９％以上となる領域が、成形過程において工具によって挟持されない必要がある。なお、本発明において、「挟持される」とは、鋼板の両面側から工具による力が加わり、高い面圧を受けている状態をいい、片面側のみが工具に接触している状態は除くものとする。 Therefore, in the powdering resistance evaluation method according to the present invention, it is necessary that the region where the amount of compressive strain on the surface of the plated steel sheet by forming becomes 9% or more is not sandwiched by the tool during the forming process. In the present invention, “clamped” refers to a state in which a force is applied by the tool from both sides of the steel plate and receives a high surface pressure, and excludes a state in which only one side is in contact with the tool. And
また、耐パウダリング性に著しく劣るめっき鋼板では、圧縮ひずみ量が約３％でもパウダリングがわずかに生じる場合がある。そのため、剥離しためっき粉の再付着の問題をより確実に防止するためには、成形によるめっき鋼板の表面の圧縮ひずみ量が３％以上となる領域が、成形過程において工具によって挟持されないことが好ましい。 Further, with a plated steel sheet that is remarkably inferior in powdering resistance, powdering may occur slightly even when the compressive strain amount is about 3%. Therefore, in order to more reliably prevent the problem of reattachment of the peeled plating powder, it is preferable that the region in which the amount of compressive strain on the surface of the plated steel sheet is 3% or more is not sandwiched by a tool in the forming process. .
本発明における耐パウダリング性評価方法で用いられるめっき鋼板の成形については、上記の条件を満たす成形であれば特に制限はない。例えば、図３に示すように、円板状に加工しためっき鋼板１を、逆円錐形のダイス２と先端形状が半球状のパンチ３とでコニカルカップ状にプレス成形することで、めっき鋼板に上記の条件を満足する成形を施すことができる。 The forming of the plated steel sheet used in the powdering resistance evaluation method of the present invention is not particularly limited as long as it satisfies the above conditions. For example, as shown in FIG. 3, a plated steel plate 1 processed into a disk shape is press-formed into a conical cup shape with an inverted conical die 2 and a punch 3 having a hemispherical tip shape. Molding that satisfies the above conditions can be performed.
ダイス２とパンチ３とによるプレス成形では、めっき鋼板は外縁側ほど、円周方向に高い圧縮ひずみ量を受け、半球状のパンチ３と接触する中心付近は引張ひずみを受けることになる。そのため、図３の右側に示される、めっき鋼板がダイスとパンチとで挟持される部分１１は、圧縮ひずみが小さく、パウダリングがほとんど発生しない。一方、外縁側のパウダリングが発生する圧縮ひずみ量が９％以上となる領域１２は、パンチと接触することがないため、面圧がほとんどかからず剥離しためっき粉の再付着等の問題が生じることがない。 In press forming with the die 2 and the punch 3, the plated steel sheet receives a higher amount of compressive strain in the circumferential direction toward the outer edge side, and the vicinity of the center in contact with the hemispherical punch 3 receives tensile strain. Therefore, the portion 11 shown on the right side of FIG. 3 where the plated steel plate is sandwiched between the die and the punch has a small compressive strain and hardly generates powdering. On the other hand, in the region 12 where the amount of compressive strain at which outer side powdering occurs is 9% or more, there is no contact with the punch. It does not occur.
成形に用いられる工具の形状および寸法について特に制限は設けないが、ＪＩＳ Ｚ ２２４９（２０１０）で規定されるコニカルカップ試験方法で使用されるダイスおよびパンチを用いることができる。この際、圧縮変形が生じる面積、つまり耐パウダリング性を評価する面積をできる限り大きくとるには、割れやしわが生じない範囲で、工具および試験片寸法をできるだけ大きくすることが望ましい。例えば、ＪＩＳ Ｚ ２２４９（２０１０）で規定されるコニカルカップ試験方法では、２７型の工具を用いることが望ましい。 There are no particular restrictions on the shape and dimensions of the tool used for molding, but dies and punches used in the conical cup test method defined in JIS Z 2249 (2010) can be used. At this time, in order to make the area where compressive deformation occurs, that is, the area for evaluating the anti-powdering property as large as possible, it is desirable to make the tool and test piece dimensions as large as possible without causing cracks and wrinkles. For example, in the conical cup test method defined in JIS Z 2249 (2010), it is desirable to use a 27-type tool.
高精度の耐パウダリング性の評価を行うためには、一定の条件での成形が望ましく、成形に際してコニカルカップにしわが生じるのを抑制するのが望ましい。そのためには、試験片となるめっき鋼板の直径は、ＪＩＳ Ｚ ２２４９（２０１０）で規定される試験片直径より小さくするのが望ましい。ＪＩＳ Ｚ ２２４９（２０１０）で規定される試験片の直径ｄ０とパンチ直径ｄ１との間には、概ね下記（Ｉ）式の関係が成り立つ。
ｄ０＝３×ｄ１−２ ・・・（Ｉ）
In order to evaluate the powdering resistance with high accuracy, it is desirable to mold under certain conditions, and it is desirable to suppress wrinkling of the conical cup during molding. For that purpose, it is desirable to make the diameter of the plated steel sheet to be a test piece smaller than the test piece diameter defined by JIS Z 2249 (2010). The relationship of the following formula (I) is generally established between the diameter d 0 of the test piece defined in JIS Z 2249 (2010) and the punch diameter d 1 .
d 0 = 3 × d 1 −2 (I)
したがって、本発明の評価方法に用いられるめっき鋼板の直径ｄ０は、パンチ直径ｄ１との間で、下記（II）式の関係を満たすことが望ましい。一方、ｄ０がｄ１に対して小さすぎると耐パウダリング性を評価する面積が小さくなり過ぎるため、下記（III）式を同時に満足することが望ましい。
ｄ０＜３×ｄ１−２ ・・・（II）
ｄ０≧１．５×ｄ１ ・・・（III）
Therefore, it is desirable that the diameter d 0 of the plated steel sheet used in the evaluation method of the present invention satisfies the relationship of the following formula (II) with the punch diameter d 1 . On the other hand, if d 0 is too small with respect to d 1 , the area for evaluating the powdering resistance becomes too small, so it is desirable to satisfy the following formula (III) at the same time.
d 0 <3 × d 1 −2 (II)
d 0 ≧ 1.5 × d 1 (III)
図４および５は、ＪＩＳ Ｚ ２２４９（２０１０）で規定される形状・寸法の工具に対して、種々の寸法の円板状めっき鋼板を用いた際にしわが生じずにコニカルカップ成形できた範囲を示したものである。なお、成形試験には合金化度８．０〜１１．８％の２７０ＭＰａ級合金化溶融亜鉛めっき鋼板（鉄鋼連盟規格：ＪＡＣ２７０Ｄ）を用い、図４に示した試験の供試材の板厚は０．５ｍｍ、図５に示した試験の供試材の板厚は０．６ｍｍとした。 4 and 5 show the range in which a conical cup can be formed without generating wrinkles when using a disk-shaped plated steel sheet of various dimensions with respect to a tool having the shape and dimensions specified in JIS Z 2249 (2010). It is shown. In the forming test, a 270 MPa class galvannealed steel sheet (iron and steel federation standard: JAC270D) having an alloying degree of 8.0 to 11.8% was used, and the thickness of the test material shown in FIG. The plate thickness of the test material of 0.5 mm and the test shown in FIG. 5 was 0.6 mm.
図４および５に示された範囲の条件でコニカルカップ成形を行うことで、簡易かつ高精度の耐パウダリング性の評価が可能となる。 By performing conical cup molding under the conditions in the range shown in FIGS. 4 and 5, it is possible to easily and highly accurately evaluate the resistance to powdering.
さらに、めっき鋼板とパンチとの間に、しわ抑制用の鋼板を介在させた状態でプレス成形を行うことで、試験片のめっき鋼板の変形がしわ抑制用鋼板の変形に追従することにより、より確実にしわの発生を抑制することができるようになる。しわ抑制用の鋼板を利用する場合、しわ抑制用鋼板単体でコニカルカップ成形した際にしわが生じない板厚であり、かつ、試験片のめっき鋼板と同じ円板状であって、前記めっき鋼板より板厚の厚い鋼板を用いるのが良い。 Furthermore, by performing press molding with a wrinkle-suppressing steel plate interposed between the plated steel plate and the punch, the deformation of the plated steel plate of the test piece follows the deformation of the wrinkle-suppressing steel plate. The generation of wrinkles can be reliably suppressed. When using a wrinkle-suppressing steel sheet, the wrinkle-suppressing steel sheet itself has a thickness that does not cause wrinkles when conical cup-molded, and is the same disk shape as the plated steel sheet of the test piece, It is preferable to use a thick steel plate.
また、しわ抑制用の鋼板の寸法は、試験片のめっき鋼板の直径と同じであることが好ましい。これは、しわ抑制用の鋼板が試験片のめっき鋼板よりも小さいと、しわ抑制用の鋼板が当たっていない外縁から、しわが発生しやすいためである。一方、しわ抑制用の鋼板が試験片のめっき鋼板よりも大きいと、しわ抑制用の鋼板が試験片のめっき鋼板から離れた状態で材料がダイス３にセットされるため、しわ抑制用の鋼板が先に円錐状に変形する。そのため、成形初期では、試験片のめっき鋼板の外縁部がしわ抑制用鋼板と接触しない状態で変形するので、試験片のめっき鋼板の外縁からしわが発生しやすくなる。 Moreover, it is preferable that the dimension of the steel plate for wrinkle suppression is the same as the diameter of the plated steel plate of a test piece. This is because when the steel sheet for wrinkle suppression is smaller than the plated steel sheet of the test piece, wrinkles are likely to occur from the outer edge that is not hit by the steel sheet for wrinkle suppression. On the other hand, if the steel sheet for wrinkle suppression is larger than the plated steel sheet of the test piece, the material is set on the die 3 in a state where the steel sheet for wrinkle control is separated from the plated steel sheet of the test piece. First deformed into a conical shape. Therefore, at the initial stage of forming, the outer edge portion of the plated steel sheet of the test piece is deformed in a state where it does not come into contact with the wrinkle suppressing steel sheet, so that wrinkles are likely to occur from the outer edge of the plated steel sheet of the test piece.
加えて、試験片のめっき鋼板がしわを発生させる駆動力に抗するために、しわ抑制用の鋼板の引張強さは、試験片のめっき鋼板以上の引張強さを有していることが好ましい。さらに、しわ抑制用の鋼板は、評価結果にしわ抑制用の鋼板のパウダリングが混入しないように、非めっき材であることが好ましい。 In addition, in order to resist the driving force that the plated steel sheet of the test piece generates wrinkles, it is preferable that the tensile strength of the steel sheet for wrinkle suppression has a tensile strength higher than that of the plated steel sheet of the test piece. . Furthermore, the wrinkle-suppressing steel plate is preferably a non-plated material so that the evaluation result does not include powdering of the wrinkle-suppressing steel plate.
図６は、同じ直径のめっき鋼板としわ抑制用鋼板とを重ねた状態で、めっき鋼板がダイス側、しわ抑制用鋼板がパンチ側になるようにプレス成形した際の、しわが生じずにコニカルカップ成形できた範囲を示したものである。なお、供試材は、図４に示した試験と同じ合金化度８．０〜１１．８％の板厚０．５ｍｍの２７０ＭＰａ級合金化溶融亜鉛めっき鋼板（鉄鋼連盟規格：ＪＡＣ２７０Ｄ）であり、しわ抑制用の鋼板は板厚１．４ｍｍの５９０ＭＰａ級の鋼板とした。 FIG. 6 shows a conical shape without wrinkling when press-molded so that the plated steel sheet is on the die side and the wrinkle suppressing steel sheet is on the punch side in a state where the plated steel sheet and the wrinkle suppressing steel sheet are stacked with the same diameter. The range in which the cup could be formed is shown. The test material is a 270 MPa class alloyed hot-dip galvanized steel sheet (steel federation standard: JAC270D) having the same alloying degree of 8.0 to 11.8% and a plate thickness of 0.5 mm as shown in FIG. The wrinkle suppressing steel plate was a 590 MPa grade steel plate having a thickness of 1.4 mm.
図４および６を比較すると、しわ抑制用鋼板を用いることによって、しわを生じずにコニカルカップ成形可能な寸法範囲が広がることが分かる。 Comparing FIGS. 4 and 6, it can be seen that the use of the wrinkle-suppressing steel sheet increases the size range in which conical cup molding can be performed without causing wrinkles.
また、ＪＩＳ Ｚ ２２４９（２０１０）に規定のコニカルカップ試験方法では、カップの底部が破断するまで成形を行うとされているが、耐パウダリング性の評価においては、コニカルカップは破断させない方が望ましい。そのため、成形ストロークＬは適宜調整することが好ましい。 Further, in the conical cup test method defined in JIS Z 2249 (2010), it is said that molding is performed until the bottom of the cup breaks. However, in the evaluation of the resistance to powdering, it is desirable not to break the conical cup. . Therefore, it is preferable to adjust the molding stroke L appropriately.
成形ストロークＬが大きすぎる場合、成形過程でコニカルカップが破断するおそれがある。また、破断しなかったとしてもめっき鋼板がダイスから抜け落ちてしまうと耐パウダリング性を評価する部分である円錐部がなくなってしまうおそれがある。一方、安定的に圧縮ひずみを９％以上生じさせ、かつ、試行回数間のバラつきを抑制するには、パンチ３の半球部分の一部が、ダイス２下側の開口部まで進入していることが好ましい。そのため、成形ストロークＬの範囲は、下記（IV）式を満足することが望ましい。
（ｄ０−ｄ２）／２×ｔａｎ（（１８０°−θ）／２）≦Ｌ≦（ｄ０−ｄ２）／２×ｔａｎ（（１８０°−θ）／２）＋ｄ１／２＋（ｄ０／２−ｄ１×π／４） ・・・（IV）
If the molding stroke L is too large, the conical cup may break during the molding process. Moreover, even if it does not break, if the plated steel sheet falls out of the die, there is a possibility that the conical portion, which is a part for evaluating the powdering resistance, may disappear. On the other hand, in order to stably generate a compressive strain of 9% or more and to suppress the variation between trials, a part of the hemispherical portion of the punch 3 has entered the opening below the die 2. Is preferred. Therefore, it is desirable that the range of the molding stroke L satisfies the following formula (IV).
(D 0 -d 2) / 2 × tan ((180 ° -θ) / 2) ≦ L ≦ (d 0 -d 2) / 2 × tan ((180 ° -θ) / 2) + d 1/2 + ( d 0 / 2-d 1 × π / 4) (IV)
形成速度について特に制限はないが、作業効率および破断防止の観点からは１０〜２００ｍｍ／ｓとするのが好ましく、３０〜１８０ｍｍ／ｓとするのがより好ましい。 Although there is no restriction | limiting in particular about formation speed, From a viewpoint of work efficiency and fracture prevention, it is preferable to set it as 10-200 mm / s, and it is more preferable to set it as 30-180 mm / s.
２．めっき剥離量の測定
本発明における耐パウダリング性評価方法で用いられるめっき剥離量の測定方法については、特に制限はなく、例えば以下に示す方法を用いることができる。
2. Measurement of plating peeling amount There is no particular limitation on the plating peeling amount measuring method used in the powdering resistance evaluation method of the present invention, and for example, the following method can be used.
（Ａ）剥離重量の測定
成形前後の重量差から剥離しためっき粉の重量を測定する方法である。具体的には、以下の手順により行う。
(A) Measurement of peeling weight This is a method for measuring the weight of the plating powder peeled from the weight difference before and after molding. Specifically, the following procedure is performed.
まず成形前のめっき鋼板を超音波洗浄等により脱脂し、精密量りを用いて重量の測定を行う。次に必要に応じて潤滑油等を塗布した後、成形を行う。そして、再度超音波洗浄等により脱脂処理と同時にパウダリングにより剥離しためっき粉を除去する。最後に精密量りを用いて重量の測定を行い、成形の前後の重量差を計算する。 First, the plated steel sheet before forming is degreased by ultrasonic cleaning or the like, and the weight is measured using a precise weighing. Next, after applying lubricating oil etc. as needed, it shape | molds. And the plating powder which peeled by powdering is removed simultaneously with a degreasing process by ultrasonic cleaning etc. again. Finally, the weight is measured using a precision weight, and the weight difference before and after molding is calculated.
（Ｂ）テープ剥離法
成形品のパウダリング発生個所にテープを貼り付けて、テープに付着しためっき粉の色の濃淡から耐パウダリング性を評価する方法である。この方法を用いる場合、上述の曲げ試験による評価では、パウダリングが曲げ部のみのわずかな領域で発生するため、測定者によるばらつきが生じ得る。しかし、コニカルカップ成形試験による評価では、カップ内側の広い部分にパウダリングが発生するため、測定者によるばらつきを低減でき、かつ、カップ外縁ほど大きな圧縮ひずみが生じて、圧縮ひずみが傾斜的に分布するので、広い範囲の合金化度の材料に対して精度の高い評価が可能となる。
(B) Tape peeling method This is a method for evaluating the powdering resistance from the shade of the color of the plating powder adhering to the tape by attaching the tape to the part where powdering occurs in the molded product. When this method is used, in the evaluation by the above-described bending test, powdering occurs in a small region of only the bent portion, and therefore, variation by the measurer may occur. However, in the evaluation by the conical cup molding test, powdering occurs in a wide part inside the cup, so that the variation by the measurer can be reduced, and the outer edge of the cup causes a larger compressive strain, and the compressive strain is distributed in a gradient manner. Therefore, highly accurate evaluation is possible for materials having a wide range of alloying degrees.
また、テープの画像をスキャンしてＰＣに取り込み、適宜画像処理を行うことで測定者間の誤差をより低減させることが可能となる。この方法では、例えば、テープの色の濃淡を２５６段階で判定した後、任意の閾値を設けて二諧調処理して濃い部分と薄い部分とに区分し、その面積率を耐パウダリング性の指標として評価することができる。 Further, it is possible to further reduce errors between measurers by scanning an image on a tape and taking it into a PC and appropriately performing image processing. In this method, for example, after determining the color tone of the tape in 256 levels, an arbitrary threshold value is provided and the two-tone process is performed to classify the area into a dark portion and a thin portion, and the area ratio is an index for anti-powdering property. Can be evaluated as
以下、実施例によって本発明をより具体的に説明するが、本発明はこれらの実施例に限定されるものではない。 EXAMPLES Hereinafter, although an Example demonstrates this invention more concretely, this invention is not limited to these Examples.
合金化度が異なる６種類のめっき鋼板を用いてコニカルカップ成形試験を行い、耐パウダリング性評価方法の精度の検証を行った。供試材は、いずれも板厚０．７ｍｍ、めっき目付量が５０〜６０ｇ／ｍ２の２７０ＭＰａ級合金化溶融亜鉛めっき鋼板（鉄鋼連盟規格：ＪＡＣ２７０Ｄ）であり、合金化度がそれぞれ、８．０％、９．６％、１０．６％、１１．０％、１１．０％および１１．８％である。 A conical cup forming test was conducted using six types of plated steel sheets with different degrees of alloying, and the accuracy of the powdering resistance evaluation method was verified. Each of the test materials is a 270 MPa class alloyed hot-dip galvanized steel sheet (iron and steel federation standard: JAC270D) having a thickness of 0.7 mm and a coating weight of 50 to 60 g / m 2 , and the degree of alloying is 8. 0%, 9.6%, 10.6%, 11.0%, 11.0% and 11.8%.
コニカルカップ成形試験には、ＪＩＳ Ｚ ２２４９（２０１０）で規定される２７型の工具を用いた。すなわち、ダイス開き角度θが６０°、ダイス穴直径ｄ２が３２ｍｍ、パンチ直径ｄ１が２６．９９ｍｍである。一方、試験片であるめっき鋼板の直径ｄ０は、２７型の試験片直径である７８ｍｍより小さい５６ｍｍとした。 In the conical cup molding test, a 27-type tool defined in JIS Z 2249 (2010) was used. That is, the die opening angle θ is 60 °, the die hole diameter d 2 is 32 mm, and the punch diameter d 1 is 26.99 mm. On the other hand, the diameter d 0 of the plated steel sheet as the test piece was set to 56 mm, which is smaller than the 78-inch test piece diameter of 78 mm.
成形ストロークＬは、コニカルカップの破断が生じないように３３．２ｍｍとし、成形速度は１、１０、１００および５００ｍｍ／ｓの４種類で試験を実施した。 The molding stroke L was 33.2 mm so that the conical cup was not broken, and the molding speed was 1, 10, 100 and 500 mm / s.
めっき剥離量の測定は、前述の（Ａ）剥離重量の測定（成形前後の試験片の重量比較）および（Ｂ）テープ剥離法（テープ画像の２値化処理）の２種類により行った。 The plating peeling amount was measured by the above-mentioned (A) measurement of peeling weight (weight comparison of test pieces before and after molding) and (B) tape peeling method (binarization processing of tape image).
図７は、それぞれの成形速度でのめっき剥離量（ｍｇ）と合金化度（％）との関係を示した図である。なお、図中のエラーバーは、試行回数は３回での標準偏差を示したものである。 FIG. 7 is a graph showing the relationship between the plating stripping amount (mg) and the degree of alloying (%) at each forming speed. The error bars in the figure indicate the standard deviation when the number of trials is three.
図７から明らかなように、いずれの成形速度においても合金化度の増加に伴い、めっき剥離量が増加する傾向が明瞭に認められ、さらにばらつきも小さく、特に成形速度が１０および１００ｍｍ／ｓの時にばらつきが極めて小さくなった。したがって、本発明に係る耐パウダリング性の評価方法は精度が高いことが分かる。 As can be seen from FIG. 7, the tendency to increase the amount of plating peeling with the increase in the degree of alloying is clearly observed at any forming speed, and the variation is small, especially when the forming speed is 10 and 100 mm / s. Sometimes the variation was very small. Therefore, it can be seen that the powdering resistance evaluation method according to the present invention has high accuracy.
また、図８は、成形速度１０ｍｍ／ｓでコニカルカップ成形した時の、カップ内側面をテープ剥離した後のテープ画像と合金化度（％）との関係を示した図である。なお、画像の２値化処理においては、テープの色の濃淡を２５６段階で判定した後、１７０以上を白、１６９以下を黒と判定し、黒色面積率を算出した。このように、テープ剥離法によっても、めっき鋼板の耐パウダリング性を定量的に精度良く評価できることが分かる。 FIG. 8 is a graph showing the relationship between the tape image after peeling the inner surface of the cup and the degree of alloying (%) when conical cup molding is performed at a molding speed of 10 mm / s. In the binarization processing of the image, after determining the color density of the tape in 256 stages, 170 or more was determined to be white and 169 or less was determined to be black, and the black area ratio was calculated. Thus, it can be seen that the powdering resistance of the plated steel sheet can be quantitatively and accurately evaluated by the tape peeling method.
本発明によれば、めっき鋼板の表面にパウダリングを発生させる成形を行うに際して、剥離しためっき粉の再付着が生じることがないため、めっき剥離量を簡易かつ高精度に測定することが可能である。 According to the present invention, when performing forming that generates powdering on the surface of the plated steel sheet, the peeled-off plating powder does not reattach, so that the amount of plating peeling can be measured easily and with high accuracy. is there.
１．めっき鋼板
２．ダイス
３．パンチ
１１．工具によって挟持される部分
１２．圧縮ひずみ量が９％以上となる領域
Ｌ：成形ストローク
θ：ダイス開き角度
ｄ０：めっき鋼板の直径
ｄ１：パンチ直径
ｄ２：ダイス穴直径
1. 1. Plated steel sheet Dice 3. Punch 11. Part clamped by tool 12. Region where compression strain amount is 9% or more L: Forming stroke θ: Die opening angle d 0 : Diameter of plated steel sheet d 1 : Punch diameter d 2 : Die hole diameter
Claims (3)
前記めっき剥離量を測定する箇所は、成形過程において該工具によって挟持されない箇所であり、
円板状に加工しためっき鋼板を、逆円錐形のダイスと先端形状が半球状のパンチとでコニカルカップ状にプレス成形することで、前記めっき鋼板に前記成形が施されることを特徴とするめっき鋼板の耐パウダリング性評価方法。 Powdered steel sheet is formed by using a tool to generate powdering by generating compressive strain on at least a part of the surface of the plated steel sheet and measuring the amount of plating peeling. Is a method for evaluating
Point of measuring the plating peeling amount Ri portions der not held by the tool in the molding process,
The plated steel sheet was processed into a disk shape, die and tip shape of the inverted cone shaped by press-molding the conical cup and hemispherical punch, characterized in Rukoto said forming is performed on the plated steel sheet Method for evaluating powdering resistance of plated steel sheet.
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